I don't know what you were using to test, but the obvious solution would be to put it back in the oven unless the meat juices were running clear and the chicken otherwise seemed to be done. In which case, I hope you gobbled it up.

Did you rinse the chicken before cooking (and then pat dry afterwards)? Was the blood in the cavity congealed or still runny? Was it a chicken with the giblets inside in a plastic bag, the bag melted and the giblets made a puddle (don't ask me how I know this can happen).

It's been ages since I cooked a bird on it's back, I tend to use the stand up cooker, where it looks like the chicken is dancing in the oven. This allows most of the fat to drip out and yet the meat still be moist. But it sounds like it either needed longer cooking or something went wrong with the prep.